Dredging equipment



1964 c. D. RAMSDEN ETAL 3,152,409

DREDGING EQUIPMENT 5 Sheets-Sheet 1 Filed July 23, 1962 INVENTORS N Nw mTR vE WHE N E30 0 AORK T w v T DJGR /V A EL LEMP H n i. H M ML T RWO1964 c. D. RAMSDEN ETAL 3,

DREDGING EQUIPMENT 5 Sheets-Sheet 2 Filed July 23, 1962 5 SN Y E E mo NNSF-EN EMBSO R m WJR T DJ mm PA MM. m fim E ASLE H WWW r Oct. 13, 1964c. D. RAMSDEN ETAL 3,152,409

DREDGING EQUIPMENT 5 Sheets-Sheet 5 Filed July 23-, 1962 0 my w R: E ESNN AOR WRRF 0 I .6 T

L am T LM I. LEAD: R R AMME E mRmm M Y B 1964 c. D. RAMSDEN ETAL 3, 9

DREDGING EQUIPMENT Filed July 23, 1962 5 Sheets-Sheet 4 INVENTORSCHARLES 0. RAMSDEN RUSSELL J. ROBERTSON By WILLIAM G. FRASER OLE P.ERICKSON WWW THE IR ATTORNEYS C. D. RAMSDEN ETAL DREDGING EQUIPMENT 5Sheets-Sheet 5 Filed July 25, 1962 3 N Y 0 P. MMBR N mD E 8530 0 fi rWRRFG M aJam w EL E LEAP. H mxufl T L mfimm Y B United States Patent3,152,409 DREDGIN G EQUIPMENT Charles D. Ramsden, Alameda, and RussellJ. Robertson, San Leandro, Calif, William G. Fraser, Tampa, Fla, and OleP. Erickson, Castro Valley, Calif, assignors to Pacific CoastEngineering Company, a corporation of California Filed July 23, 1962,Ser. No. 211,493 13 Claims. (CI. 37-61) Our invention relates to underWater dredging and more particularly to improved dredging equipment forsuch purpose.

Barges designed for dredging purposes, conventionally utilize a dredgepump or pumps of the centrifugal type. A centrifugal pump for suchpurposes can be designed and built to produce a discharge pressure whichis only limited by practical considerations of cost, power requirementsand physical size. However, a centrifugal pump is limited in its abilityto provide suction pressure or vacuum pressure by the fact that themaximum theoreical vacuum pressure is a perfect vacuum of 29 to 30inches of mercury. Regardless of size, power, or other designconsiderations in the pump, the suction pressure cannot exceedatmospheric pressure as represented by the creation of a perfect vacuumat the intake or suction side of the pump.

A practical design of a dredge pump produce an effective vacuum pressureof the order of 23 to 26 inches of mercury. For a successful dredgingoperation, the velocity of the fluid mixture flowing through the suctionpipe to the pump must be sufficiently high to carry and trans port thesolid matter such as sand, gravel and rock, usually found in suspension.This suction pipe velocity is normally held at a minimum of 8 to 12 feetper second as a result of both laboratory tests and practicalexperience.

The differential pressure created between the existing atmosphericpressure and the negative suction pressure developed at the suction sideof the pump is the only force available to perform two basic functions,namely (1) to overcome frictional losses occurring as the water andsolid mixture enters the suction line and is transmitted therealong tothe centrifugal pump itself, and (2) to provide power in the form ofvelocity and pressure to physically elevate the specific weight of solidmaterial from the bottom of the body of the water up to the dredge pump.

It follows from this that the more friction losses there are in thesuction line, the less power is available for lifting solid material.Thus, the dredge designer attempts to reduce friction losses byproviding the largest diameter and shortest length of suction linepossible, consistent with requirements for a suction pipe velocitysufficient to lift, carry in suspension, and transport the mixture ofWater and solids in suspension therein.

If it were possible to eliminate all friction losses in the suctionline, the full available suction pressure could be utilized for liftingsolids. However, such a condition cannot be achieved because of therequired rate flow in the suction line. Even if it were possible toeliminate friction losses and to utilize all of the available suctionpressure for lifting solids, there exists the maximum limit of availablepower, as represented by the creation of a perfect vacuum at the suctionside of the pump.

The power available for lifting solids in a simple hydraulic suctiondredge using a single centrifugal dredge pump mounted on the dredge hasbeen shown by calculation and actual experience when dredging atmoderate depths to be suificient to transport only 15-20 percent solidmixtures. As depths increase, the percentage of solid mixtures pumpeddecreases, until it approaches 0 3,152,409 Patented Oct. 13, 1964percent solids at feet. The limiting factor in this connection is thelimiting pressures capable of being developed at the suction side of thepump despite the fact that the dredge pump has the inherent ability topump much higher percentages of solid mixtures, if such mixtures couldbe brought to the suction inlet of the pump.

Accordingly, if some means could be provided to accomplish this underthe conditions prevailing in connection with such dredging operations,the conventional centrifugal dredge pump could be made to pump mixturesup to 50 to 60 percent solids as compared to the 15 to 20 percent solidsunder the previously existing conditions. This could double the outputof a given pump, or in the alternative, a comparable output could berealized with a pump of smaller size than previously deemed necessary.

By the same token, if it were possible by practical means, to bring thesolids in suspension to the suction side of the pump, dredging atgreater depths can be made possible, for example, to depths beyond 140feet which appears to be the practical limit of present day equipment.

Among the objects of the present invention are:

(1) To provide novel and improved dredging equipment;

(2) To provide novel and improved dredging equipment capable ofconsiderably increased output capacity over and above that of priorequipment of comparable s1ze;

(3) To provide novel and improved dredging equipment of substantiallylighter weight than prior equipment of comparable output capacity;

(4) To provide novel and improved pump means for dredging;

(5) To provide novel and improved dredging equipment for dredging todepths considerably beyond that of prior equipment of like type.

Additional objects of our invention will be brought out in the followingdescription of a preferred embodiment of the same, taken in conjunctionwith the accompanying drawings, wherein:

FIGS. 1A and 1B together constitute a side view in elevation of dredgingequipment embodying the features of the present invention;

FIGS. 2A and 2B, together constitute a plan view of the equipmentdepicted in FIGS. 1A and 1B;

FIG. 3 is a view partly in section, depicting details of a jet pumpassembly and associated cutter constituting important features of thedredging equipment of the preceding figures;

FIG. 4 is a transverse view taken in the plane 44 of FIG. 3:

FIG. 5 is a transverse view taken in the plane 5-5 of FIG. 3:

FIG. 6 is a longitudinal view, partly in section, depict ing withgreater clarity, jet construction details of the jet pump assembly ofFIG. 3; and

FIG. 7 is a View in section taken in the plane 7-7 of FIG. 6.

Referring to the drawings for details of our invention in its preferredform, all the power equipment is installed on a barge 1 having parallelspaced forward extensions 3 and 5, leaving a channel '7 of exposed waterbetween them, for the anchored end of a digging ladder 9, which ishingedly secured to the barge by a hinge mounting, thus permitting ofthe digging ladder being lowered and raised with respect to a horizontalstored position.

This digging ladder, in the main, is of girder construction involvingfour longitudinal corner members 15, 17, 19, 21, inter-connected by alattice work of angle iron members 25. At the barge end, the ladderincludes tapered side plates 29, with the two upper corner members and17 extending therealong and terminating in shaft bearing 31 for hingedlysecuring the digging ladder at the barge.

On the median axis of the barge and at substantially water level, aconventional centrifugal type dredge pump 35 is mounted and powered by aprime mover 37 coupled thereto. This pump is the main pump, there beingauxiliary pump equipment involved in the system to which reference willlater be made. A suction line 41 connected at one end to this main pump,is formed with an intermediate flexible section 43 to permit the suctionline to pass longitudinally into and along the digging ladder and flexwith each hinge movement of such ladder, that portion of the suctionline Within the ladder being supported therein in any suitable manner.

Supported within the ladder adjacent the outboard end thereof is a jetpump assembly 47 coupled to the suction line 4-1 of the main centrifugalpump 35 on the barge. This jet pump assembly includes a jet casting 4-9having a cylindrical interior approaching in diameter, that of thesuction line, the casting being formed with a plurality of jetpassageways 53 in the wall thereof, at equally spaced points about theperiphery of the casting, the passageways being formed to function asjets. Lining the interior of the casting from the discharge lips of thejets is a nickel alloy liner 55 to provide increased wear anddurability.

At one end, the casting is flanged for bolting to the smaller end of aVenturi 57, which, in turn, at its larger end, is bolted to the suctionline 41. The opposite end of the jet casting is likewise flanged, and tothis end, is bolted a hollow cylindrical mounting 59 for a cutter head61, such hollow cylindrical mounting including a threaded tip 63 weldedat one end within a cylindrical pipe section 65, the other end of whichis welded between an outer and inner section 67, 69 respectively of aflange for aflixing the same to the proximate end of the jet pumpassembly casting 49. The cutter head mounting is finished 01f by a liner71 anchored into position by a weld 73 at the tip of the mounting.

To operate a jet type pump, Water must be fed to the jets at highpressure, to create at the discharge end of the jets, a region ofreduced pressure, which, in turn, due to atmospheric pressure, serves tobring in Water and solid matter in suspension from the cutter head endof the line and causes it to be directed up the suction line 41 to apoint within reach of the main centrifugal pump 35.

To supply water at the needed high pressure, which may be of the orderof 200 lbs. per square inch or more, we provide an auxiliary or pressurepump 79 on the barge, preferably one of the centrifugal type, and of asize adapted to handle the requirements of the installation. This latterpump has a suction line 81, with its intake end submerged in the water.The discharge side of this pump is flow connected to a pressure housing85 surrounding and enclosing that portion of the jet casting 49 in Whichthe jet passageways are located and forms part of the jet pump assembly.

Rather than flow connect the pressure pump 79 to this pressure housingby a separate and independent pressure line, we prefer to form the uppertwo corner members 15 and 17 of the ladder, of coupled pipe sections, toprovide twin pressure lines. To each of these pressure lines, at thehinge end of the ladder, a flexible hose coupling 87 from the dischargeof the pressure pump may be connected. At the jet pump assembly housing,each of these twin pressure lines is extended through a wall of thepressure housing 85 and Welded thereto. Thus, these upper corner membersof the digging ladder, not only function as structural members of theladder, but serve the additional function of pressure lines for the jetpump assembly.

With the cutter head 61 supported on the end of its mounting 59,provision must be made for rotating the same in order for the cutterhead to function. We provide for such rotational movement of the cutterhead, by utilizing the suction line 41 of the main pump, as a drivecoupling or drive shaft, adapted to be driven from a prime mover 91 onthe barge, and through its rotation, cause rotation of the cutter head.As an alternative, the prime mover may be mounted on the ladder itself,preferably in proximity to the hinge line.

Such rotational movement of the suction line must be accomplishedwithout disturbing the ability of the suction line to function as suchand carry the water and suspended solids to Within reach of the maincentrifugal pump 35 on the barge.

Toward this end, the flexible section 43 of the main pump suction lineis terminated in a thrust box 95 supported within the digging ladder. Inan opposite wall of the thrust box, the initial section of thecontinuing suction line is rotatably anchored in suitably sealedbearings, and provided externally of the thrust box, with a gear 97which may be coupled through a suitable drive assembly 99 to the cutterdrive engine 91, which, in the embodiment illustrated, is located on oneof the forward extensions of the barge alongside the hinged end of thedigging ladder.

The thrust box serves as an end support for that portion of the suctionline extending down through the digging ladder, which at spaced pointsalong the ladder, will be rotatably supported in suitable bearingscarried within the ladder for such purpose.

Utilizing the suction line as a drive shaft for the cutter head,necessitates construction of the pressure housing of the jet pumpassembly, to permit of such rotation, without causing correspondingrotation of the pressure housing and the digging ladder to which it isconnected, for such rotation of the digging ladder, not only could notbe tolerated, but would create insurmountable problems.

Accordingly, the specific construction of the pressure housing 85 issuch as will permit rotational movement of the suction lineindependently of the pressure housing, while maintaining a proper sealedcondition between the housing and its mounting, to minimize loss ofpressure from the inside of the housing, and the probable entrance ofmurky water and abrasive from outside the housing, particularly duringquiescent periods.

Specifically, it includes a large end wall of substantially rectangularconfiguration having a large central opening 107, permitting the wall toloosely fit about the jet casting, and a smaller end wall 109 ofsubstantially circular configuration, this smaller end wall also havinga central opening 111 therethrough of sufficient size to fit over thecutter head mounting 59. An outer Wall 113 of heavy sheet metal, weldedat one end to the periphery of the large rectangular wall 105, tapers toclosely fit the circumference of the circular end wall 109 to which itis also welded.

At the location of the larger Wall, the jet casting is formed withparallel peripheral ribs 117, 119 adapted to support a bearing ring 121welded thereto against which an inturned sealing ring 123 may bemaintained in relative sliding relationship by supporting it on a flange12S bolted to the larger end wall about the circumference of the openingtherein.

At the location of the smaller end Wall of the pressure housing, asimilar flange 129 bolted about the circumference of the openingtherethrough, carries a bearing housing 131 in which is disposed aplurality of phenolic staves 133 for relative sliding contact with asleeve 135 surrounding the cutter head mounting cylinder 65 and weldedthereto, the sleeve preferably being chrome plated.

The bearing housing 131 at its inner end, which brings it within the jetor pressure housing 85, carries a sealing ring 139 in sealing engagementwith the sleeve, and exposed to the pressure of water in the pressurehousing to maintain sealing. Between this sealing ring 139 and thebearing staves 133 is a chamber 141 exposed to the admission of liquidfrom the pressure housing through small openings 143 provided in thebearing housing at this region, to effect and maintain water lubricationof the bearing staves at this end thereof.

The pressure housing is stabilized as to its location, as previouslyindicated, by its connection to the end of the digging ladder. Relativeto the specific pressure housing under consideration, such connection tothe digging ladder is effected by welding the ends of the two lowercorner members 19 and 21 of the ladder to the larger end wall at thelower corners thereof, While the twin pressure line members 15 and 17 ofthe ladder pass through the upper corners of the larger end wall, towhich they are welded.

By reason of the drive connection to the suction line, and theconstruction and manner of mounting of the pressure housing of the jetpump assembly, the suction line may be rotated and function as a driveshaft, so as to drive the cutter head, and without affecting either theability of the suction line to function as such, or to interfere withefficient supply of water at high pressure to the jets of the jet pumpassembly.

Because of the ability of the jet pump assembly to enhance the capacitycapability of the main centrifugal pump, the entire system may functionfor shallow dredging operations with substantially double the capacityof conventional available equipment of corresponding size, at the sametime, permitting of dredging to depths far in excess of that capablewith present-day conventional equipment. For example, depths of theorder of about 140 feet represent the maximum economical capability ofcomparable present-day equipment, while, with equipment constructed inaccordance with the present invention, dredging at depths exceeding 200feet and more may be readily accomplished.

When dredging at such depths, however, digging ladders of considerablelonger lengths than those previously employed, must be utilized.Conventionally, it has been the practice to support the outboard end ofsuch a digging ladder from a derrick or hoist mounted on the barge,whereby the digging ladder may be raised or lowered at will on its hingeaxis. With the longer digging ladders required through the use of thepresent invention, the tipping moment exerted by such ladder becomesquite large, and in fact could be sufficient to tip the barge up on end,unless the barge were well weighted down to counteract such tippingmoment.

In accordance with our present invention, we have eliminated all suchtipping moments regardless of the length of the digging ladder, and as aresult, avoid any need for concern as to whether the barge possessessufficient weight to counteract the tipping movement to which it mightotherwise be exposed when using conventional equipment.

We accomplish the foregoing broadly, by supporting the outboard end ofthe digging ladder in a manner which will not transfer the carried loadto the barge itself. A pair of pontoons 151, 153 of sufiicientdisplacement to support the outboard end of the digging ladder, aredisposed, one to either side of the ladder, and are maintained in suchspaced relationship by a bridge 155 connecting the two pontoons. Theresulting pontoon assembly is maintained at a distance from the barge bya pair of floating booms 157, 159, each connected at one end to thebarge, and at its other end to one of the pontoons. Rigidity is securedby means of cross cables 163, each connecting at one end to the anchorpoint of one of the floating booms, and at its other end to an uppercorner of the bridge connecting the pontoons.

Supported at an intermediate point of the bridge, is a sheave 171constituting a component of a sheave system which includes a powerdriven winch 175 located on the barge, and a sheave 177 mounted on thedigging ladder toward the outboard end thereof. A cable 179inter-coupling the winch and the aforementioned sheaves,

enables an operator on the barge to control the lifting and lowering ofthe digging ladder on its hinge axis, between a substantially horizontalposition of the digging ladder, and any depth within the range of theequipment. With the outboard end of the digging ladder thus supportedfrom the bridged pontoons, it becomes apparent that regardless of thelength of the digging ladder, the barge will not be subjected to anytipping moments.

From the foregoing description of our invention in its preferred form,it can be readily appreciated that the same fulfills all the objects ofour invention, and while we have illustrated and described the same inconsiderable detail, the same is subject to alteration and modificationwithout departing from the underlying principles involved, and weaccordingly do not desire to be limited in our protection to thespecific details illustrated and described, except as may benecessitated by the appended claims.

We claim:

1. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including atleast one jet in the wall thereof,

a pressure housing afiixed to said digging ladder and surrounding saidjet means and enclosing said jet,

means rotatably mounting said jet means with respect to said surroundingpressure housing,

additional pump means on said barge,

means directing the output of said additional pump means along saidladder to said pressure housing to pressure feed said jet,

a cutter head and means coupling the same to the outboard end of saidjet means,

means for rotating said suction line and jet means to rotate said cutterhead without interrupting the functioning of said jet pump, and

means for raising and lowering said ladder.

2. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including atleast one jet in the wall thereof,

a pressure housing afiixed to said digging ladder and surrounding saidjet means and enclosing said jet,

means rotatably mounting said jet means with respect to said surroundingpressure housing,

additional pump means on said barge,

means directing the output of said additional pump means along saidladder to said pressure housing to pressure feed said jet,

a cutter head and means coupling the same to the out board end of saidjet means,

means for rotating said suction line and jet means to rotate said cutterhead without interrupting the functioning of said jet pump,

said suction line and jet rotating means including a rotatable thrustbearing coupled in said suction line,

to divide said suction line into a non-rotating portion connecting tosaid centrifugal dredge pump, and an adjacent portion rotatable withrespect thereto and connecting with said cutter head by way of said jetmeans and said coupling means,

rotation permitting seal means between said jet means and said pressurehousing, and

means for rotatably driving the rotatable portion of said suction line,and

means for raising and lowering said ladder,

said ladder raising and lowering means including a pair of pontoons oneto either side of said ladder,

a bridge connecting said pontoons,

floating booms connecting said pontoons to said barge at a distance fromsaid barge, and

a sheave system including a Winch on said barge, a sheave on said bridgeand cables from said winch, about said sheave and to said ladder.

3. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including aplurality of jets in the wall thereof,

a pressure housing surrounding said jet means and enclosing said jets,

means rotatably supporting said jet means relative to said surroundingpressure housing,

additional pump means on said barge,

means directing the output of said additional pump means along saidladder to said pressure housing to pressure feed said jets,

a cutter head and means Coupling the same to the outboard end of saidjet means,

means for rotating said suction line and jet means to rotate said cutterhead without interrupting the functioning of said jet pump,

said suction line and jet rotating means including a rotatable thrustbearing coupled in said suction line, to divide said suction line into anon-rotating portion connecting to said centrifugal dredge pump, and anadjacent portion rotatable with respect thereto and connecting with saidcutter head by way of said jet means and said coupling means,

rotation permitting seal means between said jet means and said pressurehousing, and

means for rotatably driving the rotatable portion of said suction line,and

means for raising and lowering said ladder,

said ladder raising and lowering means including a pair of pontoons oneto either side of said ladder,

a bridge connecting said pontoons,

means connecting said pontoons to said barge at a distance from saidbarge, and

a sheave system including a winch on said barge, a sheave on said bridgeand cables from said winch, about said sheave and to said ladder.

4. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including aplurality of jets in the wall thereof,

a pressure housing surrounding said jet means and enclosing said jets,

additional pump means on said barge,

means directing the output of said additional pump means along saidladder to said pressure housing to pressure feed said jets,

a cutter head and means coupling the same to the outboard end of saidjet means,

means for rotating said suction line and jet means to rotate said cutterhead without interrupting the functioning of said jet pump,

said suction line and jet rotating means including a rotatable thrustbearing coupled in said suction line, to divide said suction line into anon-rotating portion connecting to said centrifugal dredge pump, and anadjacent portion rotatable with respect thereto and connecting with saidcutter head by way of said jet means and said coupling means,

rotation permitting seal means between said jet means and said pressurehousing, and

means for rotatably driving the rotatable portion of said suction line,

means for raising and lowering said ladder at its free end,

said ladder raising and lowering means including a pair of pontoons oneto either side of said ladder,

a bridge connecting said pontoons,

floating booms connecting said pontoons to said barge at a distance fromsaid barge, and

a sheave system including a winch on said barge, a sheave on said bridgeand cables from said winch, about said sheave and to said ladder.

5. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

said digging ladder including a pipe line as a longitudinal structuralmember thereof,

a centrifugal type dredge pump on said barge and having a. suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including atleast one jet in the wall thereof,

a pressure housing afiixed to said digging ladder with said pipelineterminating therein, said pressure housing surrounding said jet meansand enclosing said j additional pump means on said barge,

means directing the output of said additional pump means down said pipeline structural member of said ladder to said pressure housing topressure feed said j a cutter head and means coupling the same to theoutboard end of said jet means in longitudinal spaced relationship tosaid pressure housing,

means for rotating said cutter head without interrupting the functioningof said jet pump,

and means for raising and lowering said ladder.

6. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

said digging ladder including a pipe line as a longitudinal structuralmember thereof,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including aplurality of jets in the Wall thereof,

a pressure housing afl'ixed to said digging ladder with said pipelineterminating therein, said pressure housing surrounding said jet meansand enclosing said jets,

additional pump mean on said barge,

means directing the output of said additional pump means down said pipeline structural member of said ladder to said pressure housing topressure feed said jets,

a cutter head and means coupling the same to the outboard end of saidjet means,

means for rotating said cutter head without interrupting the functioningof said jet pump,

said cutter head rotating means including a rotatable thrust bearingcoupled in said suction line, to divide said suction line into anon-rotating portion connecting to said centrifugal dredge pump, and anadjacent portion rotatable with respect thereto and connecting with saidcutter head by way of said jet means and said coupling means,

and means for rotatably driving the rotatable portion of said suctionline,

and means for raising and lowering said ladder.

7. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

said digging ladder including a pipe line as a longitudinal structuralmember thereof,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including aplurality of jets in the wall thereof,

a pressure housing surrounding said jet means and enclosing said jets,

additional pump means on said barge,

means directing the output of said additional pump means down said pipeline structural member of said ladder to said pressure housing topressure feed said jets,

a cutter head and means coupling the same to the outboard end of saidjet means,

means for rotating said cutter head without interrupting the functioningof said jet pump,

said cutter head rotating means including a rotatable thrust bearingcoupled in said suction line, to divide said suction line into anon-rotating portion connecting to said centrifugal dredge pump, and anadjacent portion rotatable with respect thereto and connecting with saidcutter head by way of said jet means and said coupling means,

rotation permitting seal means between said jet means and said pressurehousing, and

means for rotatably driving the rotatable portion of said suction line,

and means for raising and lowering said ladder.

8. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted 10 to be loweredto a depth below the surface of Water on which said barge may befloating,

said digging ladder including a pipe line as a longitudinal struturalmember thereof,

a dredge pump on said barge and having a suction line extending alongand supported by said ladder,

a jet pump assembly carried by said ladder and conmeeting to saidsuction line, said jet pump assembly including at least one jet,

additional pump means on said barge, and

means directing the output of said additional pump means down said pipeline structural member of said ladder to said jet pump assembly topressure feed said jet.

9. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

said digging ladder including a pipe line as a longitudinal structuralmember thereof,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including atleast one jet in the wall thereof,

a pressure housing atfixed to said digging ladder with said structuralpipeline member terminating therein, said pressure housing surroundingsaid jet means enclosing said jet,

additional pump means on said barge, and

means directing the output of said additional pump means down said pipeline structural member of said ladder to said pressure housing topressure feed said jet.

10. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

said digging ladder being fabricated of longitudinal corner structuralmembers including a pipe line as at least one of said structural membersthereof,

a centrifugal type dredge pump on said barge and having a suction lineextending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to saidsuction line, said jet pump assembly including jet means of generallycylindrical shape flow coupled to said suction line and including aplurality of jets in the wall thereof and a lining of nickel hardenedalloy extending downstream from the lips of said jets,

a pressure housing affixed to said digging ladder with each saidpipeline terminating therein, said pressure housing surrounding said jetmeans and enclosing said jets,

additional pump means on said barge,

means directing the output of said additional pump means down each saidpipe line structural member of said ladder to said pressure housing topressure feed said jets,

a cutter head and means coupling the same to the outboard end of saidjet means,

means for rotating said cutter head without interrupting the functioningof said jet pump, said cutter head rotating means including a rotatablethrust bearing coupled in said suction line, to divide said suction lineinto a non-rotating portion connecting to said centrifugal dredge pump,and an adjacent portion rotatable with respect thereto and connectingwith said cutter head by way of said jet means and said coupling means.

11. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a dredge pump on said barge and having a suction line extending alongand supported by said ladder, and

means for raising and lowering said ladder,

said means including a float assembly and means fixedly maintaining saidfloat assembly at a distance from said barge, and

a sheave system including a winch on said barge, a sheave carried bysaid float assembly, and a cable from said winch, about said sheave andto said ladder.

12. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of Water on which said barge may be floating,

a dredge pump on said barge and having a suction line extending alongand supported by said ladder, and

means for raising and lowering said ladder,

said means including a pair of pontoons one to either side of saidladder,

a bridge connecting said pontoons,

means maintaining said pontoons at a fixed distance from said barge,said means including a pair of floating booms, each connected at one endto said barge and at its other end to one of said pontoons, and

a sheave system including a winch on said barge, a sheave on said bridgeand a cable from said winch, about said sheave and to said ladder.

13. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered toa depth below the surface of water on which said barge may be floating,

a dredge pump on said barge and having a suction line extending alongand supported by said ladder, and

means for raising and lowering said ladder,

said means including a pair of pontoons one to either side of saidladder,

a bridge connecting said pontoons,

means maintaining said pontoons at a fixed distance from said barge, and

a sheave system including a winch on said barge, a sheave on said bridgeand a cable from said Winch, about said sheave and to said ladder.

References Cited in the file of this patent UNITED STATES PATENTS632,126 Kirk Aug. 29, 1899 868,774 Goth Oct. 22, 1907 1,619,850 CaseyMar. 8, 1927 1,759,490 Neveling May 20, 1930 1,861,349 Lockett May 31,1932 FOREIGN PATENTS 851,790 Great Britain Oct. 19, 1960 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,152,409 October 13,1964 Charles D. Ramsden et al,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the grant, lines 1 to 4, for "Charles D. Ramsden, of Alameda, andRussell J. Robertson, of San Leandro, California, William G. Fraser, ofTampa, Florida, and Ole P, Erickson, of Castro Valley, California," readCharles D. Ramsden, of Alameda, Russell J, Robertson, of San Leandro,and William G, Fraser, of Castro Valley, California and Ole P. Erickson,of Tampa, Florida, in the heading to the printed specification lines 3to 5, for "Charles D, Ramsden, Alameda, and Russell J. Robertson, of.San Leandro, Calif. William G. Fraser, Tampa, Fla, and Ole P. Erickson,Castro Valley, Calif, read Charles D. Ramsden, Alameda, Russell J.Robertson, San Leandro, and William G. Fraser, Castro Valley, Calif andOle P. Erickson, Tampa, Fla.

Signed and sealed this 23rd day of February 1965.

(SEAL) Attest:

ERNEST W, SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. DREDGING EQUIPMENT COMPRISING A BARGE, A DIGGING LADDER EXTENDINGFROM SAID BARGE AND ADAPTED TO BE LOWERED TO A DEPTH BELOW THE SURFACEOF WATER ON WHICH SAID BARGE MAY BE FLOATING, A CENTRIFUGAL TYPE DREDGEPUMP ON SAID BARGE AND HAVING A SUCTION LINE EXTENDING ALONG ANDSUPPORTED BY SAID LADDER, A JET PUMP ASSEMBLY CARRIED BY SAID LADDER ANDCONNECTING TO SAID SUCTION LINE, SAID JET PUMP ASSEMBLY INCLUDING JETMEANS OF GENERALLY CYLINDRICAL SHAPE FLOW COUPLED TO SAID SUCTION LINEAND INCLUDING AT LEAST ONE JET IN THE WALL THEREOF, A PRESSURE HOUSINGAFFIXED TO SAID DIGGING LADDER AND SURROUNDING SAID JET MEANS ANDENCLOSING SAID JET, MEANS ROTATABLY MOUNTING SAID JET MEANS WITH RESPECTTO SAID SURROUNDING PRESSURE HOUSING, ADDITIONAL PUMP MEANS ON SAIDBARGE, MEANS DIRECTING THE OUTPUT OF SAID ADDITIONAL PUMP MEANS ALONGSAID LADDER TO SAID PRESSURE HOUSING TO PRESSURE FEED SAID JET, A CUTTERHEAD AND MEANS COUPLING THE SAME TO THE OUTBOARD END OF SAID JET MEANS,MEANS FOR ROTATING SAID SUCTION LINE AND JET MEANS TO ROTATE SAID CUTTERHEAD WITHOUT INTERRUPTING THE FUNCTIONING OF SAID JET PUMP, AND MEANSFOR RAISING AND LOWERING SAID LADDER.